Table 3 Being hospitalised for infection during the first year of life and the risk of later RA and JIA. Number of exposed cases/controls and relative risk of JIA, RA overall, and specifically for RF-positive and RF-negative RA

	All RA (333 cases/1332 controls)		RF-positive RA (153 cases/612 controls)		RF-negative RA (107 cases/428 controls)		JIA (3334 cases/13 336 controls)
	Exposed cases/controls	OR (95% CI)	Exposed cases/controls	OR (95% CI)	Exposed cases/controls	OR (95% CI)	Exposed cases/controls	OR (95% CI)
All infections	18/51	1.4 (0.8 to 2.5)	7/23	1.2 (0.5 to 2.9)	7/11	2.6 (1.0 to 7.0)	418/954	1.9 (1.7 to 2.1)
Respiratory	7/15	1.9 (0.8 to 4.9)	2/6	1.4 (0.3 to 7.2)	3/4	3.0 (0.7 to 13.4)	188/387	2.0 (1.7 to 2.4)
Gastrointestinal	5/12	1.7 (0.6 to 4.7)	3/4	3.0 (0.7 to 13.4)	1/3	1.3 (0.1 to 12.8)	134/241	2.3 (1.8 to 2.8)
Skin	2/3		1/1		1/1		44/116	1.5 (1.1 to 2.2)

JIA, juvenile idiopathic arthritis; OR, odds ratio; RA, rheumatoid arthritis; RF, rheumatoid factor.